Transformer with ferromagnetic circuits of unequal saturation inductions

Abstract

Ferromagnetic cores and electric transformers having a ferromagnetic core having at least two ferromagnetic circuits are described. At least one ferromagnetic circuit is composed of a ferromagnetic amorphous material and at least one ferromagnetic circuit is composed of a grain oriented electrical steel. The amorphous material having a saturation induction which is lower than that of the grain oriented steel. Methods of fabricating the core and using the transformer are also described.

We claim: 
     
       1. A ferromagnetic core, for use in a power transformer having an operation induction, B, wherein said core comprises: a plurality of ferromagnetic circuits;   said plurality of ferromagnetic circuits being constructed of at least two ferromagnetic materials having different saturation limited inductions;   a first ferromagnetic circuit of said plurality of ferromagnetic circuits being constructed of an iron base amorphous material having a saturation limited induction, B 1  ;   a second ferromagnetic circuit of said plurality of ferromagnetic circuits being constructed of a grain oriented electrical steel having a saturation limited induction, B 2  ;   and wherein said operating induction, B is between B 1  and B 2 .   
     
     
       2. The ferromagnetic core according to claim 1 wherein said second ferromagnetic circuit structurally supports said first ferromagnetic circuits. 
     
     
       3. The ferromagnetic core according to claim 1 wherein the permeability of said amorphous material is at least about 50% of the permeability of said grain oriented electrical steel at like levels of induction up to about 15 kG. 
     
     
       4. The ferromagnetic core according to claim 1 wherein the permeability of said amorphous material is at least about equal to the permeability of said grain oriented electrical steel at like levels of induction up to about 15 kG. 
     
     
       5. The ferromagnetic core according to claim 1 wherein the operating induction is between about 15 and about 18 kG. 
     
     
       6. The ferromagnetic core according to claim 1 wherein said plurality of ferromagnetic circuits are parallel and adjacent ferromagnetic circuits. 
     
     
       7. The ferromagnetic core according to claim 6 wherein said plurality of ferromagnetic circuits are concentric ferromagnetic circuits. 
     
     
       8. The ferromagnetic core according to claim 1 wherein said plurality of ferromagnetic circuits are concentric ferromagnetic circuits. 
     
     
       9. An electrical power transformer for transmitting and distributing electrical power in an electrical power system, comprising: a wound ferromagnetic core;   said core being constructed to provide a plurality of ferromagnetic circuits;   said plurality of ferromagnetic circuits being constructed of at least two ferromagnetic materials having different saturation limited inductions, a first ferromagnetic circuit of said plurality of ferromagnetic circuits being constructed of a ferromagnetic amorphous material;   a second ferromagnetic circuit of said plurality of ferromagnetic circuits being constructed of a grain oriented electrical steel in a stress relieved condition;   first and second electrical windings each disposed to link said plurality of ferromagnetic circuits;   said first and second electrical windings being adapted for connection to a source of electrical potential and to a load circuit, respectively;   and an operating induction between the saturation limited inductions of said ferromagnetic amorphous material and said grain oriented electrical steel.   
     
     
       10. The transformer according to claim 9 wherein said second ferromagnetic circuit structurally supports said first ferromagnetic circuit. 
     
     
       11. The transformer according to claim 9 wherein the permeability of said ferromagnetic amorphous material is at least equal to the permeability of said grain oriented electrical steel at like levels of induction up to about 15 kG. 
     
     
       12. An electrical power transformer for transmitting and distributing electrical power in an electrical power system, comprising: a ferromagnetic core;   said core being constructed to provide inner and outer ferromagnetic circuits;   said inner and outer magnetic circuits being constructed of ferromagnetic materials having different permeabilities at like levels of induction up to about 15 kG with the inner ferromagnetic circuit being constructed of the material having the lower permeability;   said outer ferromagnetic circuits being constructed of a ferromagnetic amorphous material;   said inner ferromagnetic circuit being constructed of a grain oriented electrical steel;   first and second electrical windings each disposed to link said inner and outer ferromagnetic circuits;   and said first and second electrical windings being adapted for connection to a source of electrical potential and to a load circuit, respectively.   
     
     
       13. The transformer according to claim 12 wherein said inner and outer ferromagnetic circuits are concentric and parallel ferromagnetic circuits. 
     
     
       14. The transformer according to claim 13 wherein said inner and outer ferromagnetic circuits are adjacent ferromagnetic circuits. 
     
     
       15. A method of operating an electrical power distribution transformer having a ferromagnetic core,   said core being constructed to provide a plurality of ferromagnetic circuits,   said plurality of ferromagnetic circuits being constructed of at least two ferromagnetic materials having different saturation limited inductions, a first ferromagnetic circuit of said plurality of ferromagnetic circuits being constructed of a ferromagnetic amorphous material,   a second ferromagnetic circuit of said plurality of ferromagnetic circuits being constructed of a grain oriented electrical steel,   and first and second electrical windings each disposed to link said plurality of ferromagnetic circuits,   said first and second electrical windings being adapted for connection to a source of electrical potential and to a load circuit, respectively, and wherein said method comprising the step of:   operating said first ferromagnetic circuit at an induction greater than the saturation limited induction of said ferromagnetic amorphous material.   
     
     
       16. The method according to claim 15 wherein said second ferromagnetic circuit is operated at an induction less than the saturation limited induction of said grain oriented electrical steel. 
     
     
       17. An electrical power transformer for transmitting and distributing electrical power in an electrical power system, comprising: a wound ferromagnetic core;   said core being constructed to provide a single inner ferromagnetic circuit and a single outer ferromagnetic circuit;   said inner and outer magnetic circuits being constructed of ferromagnetic materials having different watt losses at like levels of induction with the inner ferromagnetic circuit being constructed of the material having the higher watt losses;   said outer ferromagnetic circuit being constructed of a ferromagnetic amorphous material;   said inner ferromagnetic circuit being constructed of a grain oriented electrical steel;   first and second elecrical windings each disposed to link said inner and outer ferromagnetic circuits;   and said first and second electrical windings being adapted for connection to a source of electrical potential and to a load circuit, respectively.   
     
     
       18. The power transformer according to claim 17 further comprising: said inner ferromagnetic circuit structurally supporting said outer ferromagnetic circuit.